Calibration and verification tool and method for calibrating a detection apparatus

ABSTRACT

The calibration tool is provided for use with a detector, such as a detector for detecting trace amounts of one or more substances of interest. The calibration tool includes a body with at least one reservoir for retaining the calibration solution therein. A nib projects from the body and communicates with the reservoir. The nib can be wiped across a detection surface and the detection surface then may be presented to a detector. The detector then can be calibrated for the particular substance of interest in the calibration solution. The calibration tool may include plural reservoirs isolated from one another and plural nibs for applying the calibration solution to a detection surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to calibration tools and methods for calibratingan apparatus that is used to test for the presence of trace amounts ofsubstances of interest.

2. Description of the Related Art

Terrorism risks continue to increase at transportation facilities,government buildings, banks, restaurants, hotels and other locationswhere there is a significant flow of pedestrian or vehicular traffic. Asa result, virtually all airports and many other buildings now includeapparatus for detecting trace amounts of explosives.

Narcotics are illegal and insidious. Furthermore, it is known that manyterrorists organizations fund their terrorism through the lucrative saleof narcotics. Accordingly, many airports and other public buildingsrecognize the need to check for narcotics.

U.S. Pat. No. 5,491,337 discloses a device that employs and ion trapmobility spectrometer to test for trace amounts of contraband. The iontrap mobility spectrometer can be operated in a negative mode to testfor trace amounts of explosives. The ion trap mobility spectrometerdisclosed in U.S. Pat. No. 5,491,337 also can be operated in a positivemode to check for trace amounts of narcotics. Additionally, theapparatus of U.S. Pat. No. 5,491,337 can be switched quickly from thepositive mode to the negative mode so that a single sample can be testedfor the presence of trace amounts of either explosives or narcotics.Detectors that incorporate the technology disclosed in U.S. Pat. No.5,491,337 are marketed by GE Security, Inc. and perform very well. Thedisclosure of U.S. Pat. No. 5,491,337 is incorporated herein byreference.

Prior art detectors have used many techniques for delivering a sampleinto the detector to test the sample for substances of interest. Forexample, some detectors employ small flexible fabric-like traps that canbe wiped across a package or piece of luggage. The trap removes residuefrom the surface of the package or luggage. The trap then is placed inan apparatus, such as an ion trap mobility spectrometer, that tests theresidue on the trap for trace amounts of explosive materials ornarcotics.

Detectors that rely upon wiping a flexible fabric trap across a piece ofluggage impede the flow of pedestrians through a check point, and hencetypically are used only for spot checks. Additionally, an explosive ornarcotic detector of this type would not identify a contraband worn by apassenger or other pedestrian who was not carrying luggage.

U.S. Pat. No. 6,073,499 discloses a walk-through detector. The detectorshown in U.S. Pat. No. 6,073,499 operates under the principle that aboundary layer of air adjacent to a person is heated by the person. Thisheated air adjacent a person is less dense than air further from theperson. Less dense air rises. Accordingly, a thermal plume of air flowsup adjacent to a person. Minute particles, including particles ofexplosives or narcotics, will be entrained in this thermal plume of airand will flow upwardly from a person. The walk-through detectordisclosed in U.S. Pat. No. 6,073,499 employs an ion mobilityspectrometer or ion trap mobility spectrometer to detect microscopicparticles of interest that are likely to be entrained in the thermalplume of air flowing upwardly adjacent to a person who walks through andpauses briefly in the detector. The walk-through detector disclosed inU.S. Pat. No. 6,073,499 is very effective for detecting whether a personis carrying explosives or narcotics and whether the person has recentlyhandled explosives or narcotics. The disclosure of U.S. Pat. No.6,073,499 is incorporated herein by reference.

The walk through detector of U.S. Pat. No. 6,073,499 is extremelyeffective and operates very quickly. However, the device is large and isnot suitable for many access points.

Pending U.S. Patent Publication No. 2005/0019220 discloses a smalldetector with a slot through which a card may be swiped. This deviceoperates under the theory that trace amounts of particles of interestwill be transferred from the hand of a passenger or other pedestrian tothe card. These trace amounts of particles of interest then are removedas the card is swiped through the slot and particles removed from thecard can be analyzed to determine whether substances of interest arepresent. U.S. patent application No. 10/929,915 discloses another smalldetector apparatus that can be used quickly to detect for the presenceof substances of interest. More particularly, the detector of U.S.patent application No. 10/929,915 includes a thin metal disc or a thinmetal drum that rotates into proximity to a window. A passenger or otherpedestrian who desires access places his or her fingers on the metaldisc or drum. Residue from the fingers are transferred to the metal. Theremoval of the fingers from the metal disc or drum generates a signalthat causes the area that had been contacted to move into the detector.The metal material is heated sufficiently to vaporize residue thereonand the vaporized residue is transported into the ion trap mobilityspectrometer. The disclosures of U.S. Patent Publication No.2005/0019220 and U.S. patent application No. 10/929,915 are incorporatedherein by reference.

The above-described detectors work extremely well. However, variationsin atmospheric pressure, humidity and temperature can affect theperformance of these known detectors. For example, a detector used inDenver may function differently than a detector used in Florida.Furthermore, detectors used at any geographic location may performdifferently from day-to-day as climactic conditions change. Therefore,it is necessary to calibrate the detectors periodically to ensure thatthe detectors function with sufficient accuracy to detect trace amountsof explosives or narcotics based on a very small sample size for theambient conditions that exist on a particular day and at a particularlocation. Manufacturers of these detectors, such as GE Security, Inc.,generally recommend calibration on a daily basis, such as at the startof every work day. Devices that wipe a fabric trap across an item ofluggage are calibrated by using a calibration trap that is known to havesmall amounts of the substance of interest thereon or a substance thatis known to have a very similar signature. This calibration trap couldbe stored in a sealed container that is kept near the detector apparatusfor access by the security personnel. Calibration traps, however, arenot particularly useful for the more recent detector devices thatanalyze residue on the fingers of a person who desires access.

In view of the above, it is an object of the subject invention toprovide an inexpensive tool that can be used for calibrating acontraband detector so that the detector can accurately test forsubstances of interest.

SUMMARY OF THE INVENTION

The invention relates to a calibration tool for calibrating a detectorthat is operative for detecting small amounts of at least one substanceof interest. The calibration tool includes a reservoir for retaining acalibration solution and a dispenser for dispensing small amounts of thecalibration solution onto a region of the detector that will be testedfor the presence of at least one substance of interest.

The reservoir of the calibration tool may be contained in a handle thatis dimensioned to be held and manipulated easily by a user. Thedispenser may include a wick that has one end in communication with thereservoir and another end exposed externally on the handle

The tool further includes a closure for selectively isolating thedispenser and the reservoir within the handle to prevent excessiveevaporation of the calibration solution in the reservoir. The closure isa removable cap in a preferred embodiment of the calibration tool.However, other closures can be provided, such as a slit that opens onlyin response to pressure, a spring actuated valve or a ball bearing thatcan rotate at the end of the tool for selectively transferring thecalibration solution in much the same manner that a ball point pendispenses ink to a sheet of paper. The reservoir can include a smallplastic bladder that can be pierced during an initial use of thecalibration tool. The bladder may be replaceable as needed.

The calibration solution in the reservoir may be a solution with atleast one signature similar to the signature of at least one substanceof interest. However, the calibration solution in the reservoirpreferably is a diluted solution that includes the at least onesubstance of interest.

The detector may be operative for detecting the presence of explosives.In this situation, the calibration solution in the reservoir of thecalibration tool may comprise a diluted solution of at least one knownexplosive, such as TNT, RDX or other known plastic or non-plasticexplosive.

The detector may be operative for detecting the presence of at least onenarcotic. In this situation, for example, the calibration solution inthe reservoir of the calibration tool may comprise a diluted solution ofcocaine or other known narcotic that will be tested for.

As noted above, some detectors are operative to test in more than onemode, and specifically, a negative ion mode and a positive ion mode. Thenegative mode typically is employed to test for the presence ofexplosives, while the positive mode is operative to detect for thepresence of narcotics. The calibration tool may be configured for usewith a dual mode detector, such as the detector described above anddisclosed in U.S. Pat. No. 5,491,337. A calibration tool for a dual modedetector may have a calibration solution with two substances ofinterest.

The calibration tool may include first and second reservoirs and firstand second dispensers that communicate respectively with the reservoirs.The first reservoir and the first dispenser are isolated from the secondreservoir and the second dispenser. The first reservoir and firstdispenser preferably are for calibration and the second reservoir andsecond dispenser preferably are for verification. For example, thecalibration tool may include an elongate generally tubular body. Thefirst and second reservoirs may be disposed in the body and may beseparated from one another by at least one transverse wall. The firstdispenser may be at a first longitudinal end of the body, while thesecond dispenser may be at the second longitudinal end of the body. Thefirst reservoir preferably includes a calibration solution while thesecond reservoir preferably includes a verification solution. Thecalibration and verification solutions may be two different dilutesolutions of substances of interest. For example the calibration toolfor a single mode explosive detector may have a dilute solution of TNTin the first reservoir and a dilute solution of RDX in the secondreservoir. A calibration tool for a dual mode detector may have a dilutesolution of TNT and cocaine in the first reservoir and a dilute solutionof RDX and Ephedrine in the second reservoir.

The calibration tool with two reservoirs and two dispensers may furtherinclude first and second closures for selectively closing thecorresponding reservoirs and dispensers. The closures may be first andsecond caps or the other known closures described above, such as a slitvalve, a rolling ball or the like. The closure also can be a springbiased valve that is normally biased towards a closed condition.Pressure exerted on the end of the dispenser may open the valve topermit small amounts of the calibration solution to be dispensed.

The calibration tool is used by removing or opening the closure andapplying a small amount of the calibration solution to the samplecollection region on the detector. The detector then is operated in acalibration mode and may be adjusted accordingly so that test parametersfor the calibration solution are identified by the detector as beingassociated with the particular substance or substances of interest. Thesecond dispenser of the calibration tool then may be used to apply asmall amount of the verification solution to the sample collectionregion of the detector. The detector then may be operated to verify thatthe detector identifies the verification solution as having a differentspecies of the substance or substances of interest. The detector thenmay be calibrated further based on the ability of the detector to detectthe substance or substances of interest in the verification solution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a detector that can be used with thecalibration tool of the subject invention.

FIG. 2 is a schematic view of an ion trap mobility spectrometer of thedetector shown in FIG. 1.

FIG. 3 is a front perspective view, partly in section, of a samplecollection assembly of the detector for detecting substances of intereston a finger of a person.

FIG. 4 is a perspective view of an alternate sample collection assemblythat can be used with the calibration tool of the subject invention.

FIG. 5 is a perspective view of another alternate sample collectionassembly that can be used with the calibration tool of the subjectinvention.

FIG. 6 is a perspective view of one embodiment of a calibration tool inaccordance with the subject invention.

FIG. 7 is a longitudinal cross-sectional view of the calibration tool ofFIG. 6 with the caps thereof removed.

FIG. 8 is a schematic perspective view showing the calibration tool usedwith a detector of the type shown generally in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The calibration tool of the subject invention is intended for use with adetector that is operative for detecting small amounts of substances ofinterest, and particularly trace amounts of substances of interest thatmay be transferred from the fingers of a person to a sample collectionarea of the detector. Detectors of this type are particularly effectivefor detecting trace amounts of explosives or narcotics. One example ofsuch a detector is identified generally by the numeral 10 in FIG. 1.

The detector 10 includes an outer housing 11 and a flat panel displaymonitor 12, such as an LCD monitor. An ion trap mobility spectrometer(ITMS) is disposed within the housing 11 and is illustratedschematically in FIG. 2.

The ITMS of FIG. 2 comprises a cylindrical detector 20 having an inlet22 at one end for receiving sample air of interest borne by a carriergas which that has been doped with a low concentration vapor (typicallya few parts per million) employed as a charge transfer mediator. Moreparticularly, the inlet 22 communicates with a source of sample air ofinterest 14 and a supply of carrier gas and dopant 16 with flows ofgases to the inlet 22 being enabled by a flow generator such as a pumpillustrated schematically and identified by the numeral 18 in FIG. 2. Aheated membrane 19 formed from a microporeous refractory material orfrom dimethyl silicone is disposed near the inlet 22 and incommunication with the source of the sample of air 14 for blockingpassage of at least selected constituents of the air and for enablingpassage of other constituents of the air, including the constituents ofinterest. The sample air, carrier gas, and dopant molecules pass throughthe inlet 22 and are spread by a diffuser 24 into an ionization chamber26. The ionization chamber 26 is in the form of a shallow cylinder witha diameter D, length L, and cylindrical wall 28 of a radioactivematerial, e.g., nickel⁶³ or tritium, which emits beta particles. Inlet22 communicates with one end of the ionization chamber 26. A gridelectrode E₁ is provided at the end opposite the inlet 22, and isnormally maintained at the same potential as the inlet end and the wallsof the ionization chamber 26. Thus a largely field-free space isprovided in which electrons and ion charges build up and interact withthe sample molecules under bombardment by the beta-particles from theradioactive walls. Beyond the ionization chamber 26, the ionized samplegases pass through open electrode E₁ and into an ion drift region 30having several field-defining electrodes E₂-E_(n). A collector electrodeor plate 32 is disposed at the end of the drift region 30 for receivingthe ion samples reaching that end.

Periodically a field is established across the ionization region 26, bycreating a potential difference between the grid electrode E₁ and theinlet diffuser 24 and radioactive source 28, for about 0.1-0.2 mS, tosweep the ions through the open grid E₁ into the drift region 30 withthe assistance of the switching of the field between electrodes E₁ andE₂. The ions in the drift region 30 experience a constant electricfield, maintained by the annular electrodes E₂-E_(n), impelling themalong the region and down toward the collector electrode 32. Theelectrode 32 detects the arriving charge, and produces signals that areamplified and analyzed through their spectra in the spectrometer. Thegases exit through an outlet in the wall next to the electrode 32. Afterabout 0.2 mS the field across the ionization region 26 is again reducedto zero and the ion population is again allowed to build up in thechamber 26 preparatory to the imposition of the next field. The polarityof the fields is chosen on the basis of whether the detector is operatedin a negative or positive ion mode. When detecting explosives, anegative ion mode is usually appropriate, but when detecting narcoticsamples positive ion mode is preferred. The two modes can be operated inrapid sequence to test a single sample for both explosive and narcotics.

The detector 10 includes a sample collection apparatus that isidentified generally by the numeral 40 in FIGS. 1 and 3. The samplecollection apparatus 40 includes a housing 42 and a window 46 at aposition on the housing 42 that will face the person that is to bescanned for trace amounts of substances of interest. The window 46 isconfigured and dimensioned to receive at least part of the grippingsurface of a thumb or forefinger.

The sample collection apparatus 40 further includes a generallycylindrical drum 48 mounted in the housing 42 for rotation about an axisthat is parallel to the front face of the detector 10. Moreparticularly, the cylindrical drum 48 is disposed to be substantiallyinternally tangent with portions of the housing 42 adjacent the window46. Hence, a target area on the exterior of the drum 48 will be exposedat the window 46. The drum 48 is formed from a material that will retainresidue from the hand of a person being screened. The material of thedrum 48 also must be able to be heated quickly and repeatedly tosufficiently high temperatures for vaporizing residue received from thehand. Additionally, the material of the drum 48 should be capable ofbeing cooled quickly to prevent discomfort when a finger is placed onthe drum 48 and to maintain a desirably low cycle time for scanning. Thematerial of the drum preferably is a thin metallic material, such asaluminum or stainless steel. The thickness of the material of the drum48 is selected to facilitate rapid heating and cooling, and to permitslight inward deflection of the drum 48 in response to digital pressurecreated by a thumb or forefinger placed on or wiped across the targetarea of the drum 48 exposed at the window 46. This deflection cantrigger a pressure sensitive switch 52 to activate a scanning cycle.

The sample collection apparatus 40 further includes a motor 56 mountedto the housing and operative to rotate the drum 48. The motor 56 isconnected to the switch 52 and functions to rotate the drum 48 aselected amount in response to the sensed completion of a wipe of athumb or forefinger across portions of the drum 48 disposed in thewindow 46.

A desorber 58 is mounted to the housing 42 interiorly of and adjacent tothe drum 48. The desorber 58 rapidly heats portions of the drum 48 forvaporizing trace amounts of material transferred from the thumb orforefinger to the target area of the drum 48 that was exposed at thewindow 46. A sample transfer box 60 is mounted to the housing 42 at alocation radially aligned with the desorber 58, but disposed exteriorlyof and substantially adjacent the drum 48. The sample transfer box 60further includes a sample tube 62 that communicates with the inlet 22 ofthe ion trap mobility spectrometer of FIG. 2.

The movement of a thumb across the target area of the drum 48 exposed atthe window 46 will deflect the thin aluminum of the drum 48 and willactuate the pressure sensitive switch 52 aligned with the window 46. Theswitch 52 will cause the motor 56 to rotate the drum 48. Thus, thetarget area of the drum 48 that had been aligned with the window 46 willadvance into the narrow space between the desorber 58 and the sampletransfer box 60. The motor 56 then stops. The heated desorber 58 raisesthe temperature of the drum 48 between the desorber 58 and the sampletransfer box 60 sufficiently to vaporize residue transferred from thethumb to the drum 48. A vacuum pump 18 in the detector of FIG. 2 thenwill draw the vaporized material through the sample collection tube 62and into the detector for analysis. The ITMS will detect the presence ofsubstances of interest and will generate an appropriate signal foradditional or enhanced testing by security personnel at the checkpoint.

The sample collection apparatus can take other configurations. Forexample, FIG. 4 shows a sample collection apparatus 40A with a drum 48Amounted for rotation about an axis aligned at an angle, and preferably aright angle, to the front face of the detector 10. The window 46A issufficiently wide to place all forefingers of one hand on a portion ofthe drum 48A exposed at the window. FIG. 5 shows a detector 40B with analuminum disc 48B in place of the drum. The disc 48B rotates about asubstantially vertical axis. Other options can include a thin plate thattranslates without rotation or a flexible belt that is driven aboutrollers.

The detector 10 must be calibrated periodically to ensure that thedetector 10 will associate certain sensed peaks with certain substancesof interest under the current conditions of temperature, atmosphericpressure and humidity at the detection site. Accordingly, the detectormay be used with a calibration tool identified generally by the numeral64 in FIGS. 6-8. The calibration tool 64 includes an elongate body 66having opposite first and seconds ends 68 and 70. As shown most clearlyin FIG. 7, first and second reservoirs 72 and 74 are formed inside thebody 66 and are isolated from one another by a transverse wall 76. Acalibration solution is disposed in the first reservoir 72 and averification solution is disposed in the second reservoir 74. A firstmarker nib 78 is formed in proximity to the first end 68 of the body 66and communicates with the first reservoir 72. A second marker nib 80 isformed in proximity to the second end 70 of the body 66 and communicateswith the second reservoir 74. First and second caps 82 and 84 aremounted removably to the first and second ends 68 and 70 of the body 66for covering the first and second nibs 78 and 80 respectively. FIG. 7shows an embodiment where valves are disposed in the body forselectively placing the nibs 78 and 80 in communication with thereservoir 72 and 74. The valves normally are biased towards a closedposition, but can be opened in response to pressure exerted on the nibs78 or 80 during normal use of one end of the tool 64. However, othermeans for delivering solution from the reservoir 72 or 74 to the nibs 78or 80 can be provided, including a simple felt or foam wick that extendsfrom the reservoirs 72, 74 to the nibs 78, 80. COPIC markers distributedby Imagination International, Inc. have proved very successful for thecalibration tool 64. In this regard, COPIC markers can be purchasedempty and filled or refilled with appropriate calibration solutions.

The calibration and verification solutions preferably are in liquid formand are selected to produce a signature that will be recognized by thedetector 10 as one of the substances of interest. In this regard, apreferred calibration solution is a dilute solution of TNT and cocainein the first reservoir 72. More particularly, the preferred solvent isalcohol and most preferably methanol. The TNT and cocaine preferably arepresent in the calibration solution at concentrations of about 100nanograms of TNT and about 100 nanograms of cocaine per microliter ofsolution. The verification solution preferably includes RDX and a secondnarcotic of interest (e.g., Ephedrine) in the second reservoir 74. Theverification solution preferably has about 50 nanograms of RDX and about250 nanograms of Ephedrine per microliter of solution. The solvent forthe verification solution may be the same as the solvent for thecalibration solution.

The calibration tool 64 is used by removing the first cap 82 to exposethe first nib 78 of the calibration tool 64. The first nib 78 is wipedacross or pressed on the surface of a sample collection apparatus 40exposed at the window 46 of the detector 10 to apply a small amount ofthe calibration solution. Removal of the calibration tool 64 from thesample detection surface will activate the pressure sensitive switch 52and cause the detector 10 to proceed through a detection or calibrationcycle. The calibration solution containing a selected explosive (e.g.,TNT) and the selected narcotic (e.g., cocaine) will generate signalspikes for a specified peak time and peak height that permits thedetector 10 to be calibrated for the explosive and narcotics in thecalibration solution based on the ambient temperature, atmosphericpressure and humidity at the particular time and at the particular testlocation. The first cap 82 then is placed back on the body 66 to coverthe first nib 78. The second cap 84 then can be removed from the body 66to expose the second nib 80. The second nib 80 then can be pressedagainst or wiped across the detection surface to deposit a small amountof the verification solution that contains a second explosive (e.g.,RDX) and a second narcotic (e.g., Ephedrine). The detector then isoperated to verify that the detector identifies the substances ofinterest in the verification solution. Further calibration can beperformed if necessary.

While the invention has been described with respect to a preferredembodiment, it is apparent that various changes can be made withoutdeparting from the scope of the invention as defined by the appendedclaims. For example, the figures herein show one particularconfiguration for a calibration tool with a valve between the outlet ofthe reservoir and exterior portions of the nib. However, many otherconfigurations can be provided for the calibration tool, including felttip markers with no valves. Many of the commercially available markers,highlighters or the like can be used provided that there is someprotection against evaporation (e.g., a valve or cap) and someprotection against excessive leakage for the particular selectedviscosity of the calibration solution.

A dual-ended calibration tool is illustrated. However, a calibrationtool with a single marker can be provided.

A few examples of specific calibration and verification solutions wereidentified based on typical intended uses for the detectors. However,other calibration and/or verification solutions can be employed inaccordance with the specific application of the detector. Theconcentration of the substances of interest in the solution also can bevaried considerably in accordance with the sensitivity of the detector.Thus, less concentrated calibration solutions can be employed for adetector, such as an ion trap mobility spectrometer, that can detecttrace amounts of a substance of interest.

The calibration tool is illustrated for use with a particular detector.However, the calibration tool can be used with other detectors.

The calibration tool is particularly preferable for use with a detectorwhere a passenger or other person being screened wipes his or her fingeracross a detection surface that is to be analyzed. However, thecalibration tool also can be used with a detector that employs sampletraps or cards. In this regard, the nib of the calibration tool can bewiped across an initially clean sample trap or card that then ispresented to the detector for analysis.

These and other variations will be apparent to a person skilled in theart after having read the subject invention disclosure and theaccompanying drawings.

1. A calibration tool for calibrating a detector that is operative fordetecting whether at least one substance of interest is present in or ona sample, the calibration tool comprising: at least one reservoircontaining a selected solution with at least one substance of interesttherein; and at least one nib communicating with the reservoir forapplying a portion of the solution to a detecting surface of thedetector.
 2. The calibration tool of claim 1, wherein the solutioncontains an explosive material.
 3. The calibration tool of claim 2,wherein the solution further contains a narcotic material.
 4. Thecalibration tool of claim 1, wherein the solution contains a narcoticmaterial.
 5. The calibration tool of claim 1, wherein the at least onereservoir comprises first and second reservoirs isolated from oneanother and wherein the at least one nib comprises first and second nibscommunicating respectively with the first and second reservoirs.
 6. Thecalibration tool of claim 5, wherein the tool includes an elongate body,the first and second reservoirs being disposed in the body, the firstand second nibs being disposed at opposite respective ends of theelongate body.
 7. The calibration tool of claim 6, further comprisingfirst and second caps secured removably to the body for selectivelycovering the first and second nibs respectively.
 8. The calibration toolof claim 5, wherein the first reservoir includes a calibration solutioncontaining a first explosive material and a first narcotic therein andwherein the second reservoir includes a verification solution containinga second explosive material and a second narcotic therein.
 9. Thecalibration tool of claim 1, wherein the substance of interest ispresent in the solution with a concentration of about 50-250 nanogramsper microliter of solution.
 10. A method for calibrating a detector thatis used for detecting trace amounts of at least a first substance ofinterest, the method comprising: providing a marker with a calibrationreservoir that contains a calibration solution with a first species ofthe first substance of interest, the marker further having a calibrationnib communicating with the calibration reservoir and positioned to beexposed at an external position on the calibration tool; urging thecalibration nib against a detection surface of the detector so that aportion of the calibration solution in the calibration reservoir isapplied to the detection surface; and operating the detector forcalibrating the detector to the first substance of interest in thecalibration solution.
 11. The method of claim 10, wherein the markerfurther has a verification reservoir that contains a verificationsolution that has at least a second species of the at least onesubstance of interest, the marker further having a verification nibcommunicating with the verification reservoir and positioned to beexposed at an external position on the calibration tool, the methodfurther comprising: urging the verification nib against the detectionsurface of the detector so that a portion of the verification solutionin the verification reservoir is applied to the detection surface; andoperating the detector for verifying that the detector can identify thesecond species of the at least one substance of interest in theverification solution.
 12. The method of claim 11, wherein thecalibration reservoir further contains a first species of a secondsubstance of interest, the step of urging the calibration nib againstthe detection surface substantially simultaneously applies the firstspecies of the first substance of interest and the first species of thesecond substance of interest to the detection surface and wherein thestep of operating the detector is carried out for calibrating thedetector to the first substance of interest and the second substance ofinterest in the calibration solution.
 13. The method of claim 12,wherein the verification solution further includes a second species ofthe second substance of interest, the step of urging the verificationnib against the detection surface substantially simultaneously appliesthe second species of the first substance of interest and the secondspecies of the second substance of interest to the detection surface andwherein the step of operating the detector is carried out for verifyingthe presence of the first and second substances of interest in theverification solution.